For anyone who hasn't been keeping up, public implementations of a known IOSU exploit are now available which have reignited interest in WiiU hacks.
Likely as a side-effect of that availability, since the timing is coincident, a Brazilian team discovered* that with a two-byte modification to the ticket file of existing disc dumps, that ticket could be used to permanently install the eshop version of the same game to NAND or USB.
The advantage to that method over the Loadiine backup loader, is that once the title is installed, it's on the console's menu natively, i.e. no exploit is necessary to run the title, online play works, and loading speed is faster than running from the SD card.
*I say 'discovered' but what probably happened is that having IOSU access allowed the team to read the files from the disc, and what they discovered is that the files in the released WUD dumps differed from the files that they were reading via IOSU - consistently at those two bytes. In other words, the tickets on the discs have always been the right tickets for installing the eshop version as well, but using the extracted ticket from the disc dump didn't work because those two bytes were either dumped or stored incorrectly.
Whatever the actual discovery was, people have been having a field day installing titles on their systems, and nobody has reported that they've bricked their systems.
Cautious users suggest holding off until full custom firmware and NAND emulation are available, since unlike the exploit, these installs have a permanent effect on the system. Others note, as pbj did, that Nintendo didn't ban people on the Wii as long as they didn't alter the game, and that point, combined with the focus on Switch, makes it very low risk.
So WiiU hacking is hitting it's stride, but it still has a way to go. This week's progress makes it possible to load and run eshop versions of disc games (if they have the same title ID) but only because the disc tickets obviously can't be console-specific. Installing eshop-only titles isn't possible yet because everyone's tickets from those titles are only good on the console they're extracted from.
Have fun if you're into this kind of thing.